1. Field of the Invention
The present invention relates to a display apparatus, particularly relates to an effective technology applied to a display apparatus for displaying a picture, wherein light-emission elements are arranged to form a matrix and the picture is displayed by controlling light emissions of the light-emission elements.
2. Description of Prior Art
A matrix-type display apparatus has a plurality of rows and a plurality of columns arranged in directions orthogonal to each other. Each of the rows and the columns has a plurality of electrodes. Each intersection of any of the rows and any of the columns in the matrix-type display apparatus is referred to as a pixel. A matrix-type display apparatus displays a picture by adjusting a voltage applied to each pixel. Examples of a matrix-type display apparatus are a liquid-crystal display (LED) apparatus, a field-emission display (FED) apparatus, an electro-luminescence (EL) display apparatus and a light-emitting diode (LED) display apparatus.
As disclosed in Japanese publication of unexamined applications No.4-289644, electron emitter elements arranged in an FED apparatus each serve as a pixel. Electrons emitted from the electron emitter elements are accelerated in a vacuum before being radiated to phosphors to cause portions of the phosphors hit by the radiated electrons to emit lights.
As typical electron emitter elements used in an FED apparatus, a matrix of thin-film electron emitters is available. A thin-film electron emitter element is an electron emitter element that utilizes hot electrons generated by applying a strong electric field to an insulator.
An MIM (Metal-Insulator-Metal)-type electron emitter is a representative electron emitter. The following description explains the MIM-type electron emitter with a structure having 3 layers, namely, a top electrode, an insulator and a base electrode.
FIG. 21 is an explanatory diagram used for describing the principle of operation of an MIM-type electron emitter.
If a driving voltage is applied between a top electrode 11 and a base electrode 13 to set an electric field in a tunneling insulator 12 at a value in the range 1 to 10 MV/cm or greater, electrons in close proximity to the Fermi level in the base electrode 13 travel through the barrier by the tunneling phenomenon, becoming hot electrons injected into the conduction band of the top electrode 11.
In the tunneling insulator 12 and the top electrode 11, some of the hot electrons are scattered by interactions with a solid, losing energy.
As a result, at the time the hot electrons reach the boundary between the top electrode 11 and a vacuum 10, the hot electrons have different amounts of energy.
Some of the hot electrons having energy of an amount not smaller than a work function ("PHgr") of the top electrode 11 are emitted to the vacuum 10 while the remaining hot electrons flow into the top electrode 11.
The MIM-type thin-film electron emitter is disclosed in, among other documents, Japanese publication of unexamined applications No.9-320456.
A plurality of top electrodes 11 are arranged to form typically a column of a matrix while a plurality of base electrodes 13 are arranged to form typically a row of the matrix. A plurality of such rows and a plurality of such columns are laid out in directions orthogonal to each other to form the matrix. An intersection of a row and a column has a top electrode 11 on the column and a base electrode 13 on the row. Such an intersection is referred to as a thin-film electron emitter. Since each MIM-type thin-film electron emitter in the matrix is capable of emitting an electron beam, the thin-film electron emitter serves as an electron emitter element of a matrix-type display apparatus.
Each of the MIM-type thin-film electron emitters in the matrix is a pixel of the display apparatus. In the display apparatus with such a configuration, electrons emitted by each of the MIM-type thin-film electron emitter in the matrix are accelerated in the vacuum 10 before being radiated to phosphors to cause portions of the phosphors hit by the radiated electrons to emit lights to display a desired picture.
The thin-film electron emitter displays excellent characteristics, which qualify the electron emitter to serve as an electron emitter element for FED. The excellent characteristics include the fact that the thin-film electron emitter satisfies a requirement for implementation of a high-resolution display apparatus due to its excellence in the directionality of its emitted electron beam. Another example of the excellent characteristics is easy handling attributed to the fact that the thin-film electron emitter is not severely affected by surface contamination.
Since the display apparatus using a matrix of thin-film electron emitters employs neither a shadow mask nor beam-deflection circuitry, unlike a cathode-ray tube (CRT), the power consumption of such a display apparatus is slightly smaller than or about equal to that of a CRT display apparatus.
The power consumption of a matrix of thin-film electron emitters driven by adopting the conventional driving technique in a display apparatus employing the matrix of thin-film electron emitters is estimated as follows.
FIG. 22 is a diagram showing the configuration of the conventional matrix of thin-film electron emitters in a simple and plain manner.
A row electrode 310 stretched in the row direction is connected to one of the electrodes, that is, the base electrode 13, of each thin-film electron emitter element 301 associated with the row electrode 310. On the other hand, a column electrode 311 stretched in the column direction is connected to the other electrode, that is, the top electrode 11, of each thin-film electron emitter element 301 associated with the column electrode 311.
It should be noted that, while FIG. 22 shows the configuration of a typical matrix of 3 rowsxc3x973 columns, in actuality, the matrix has as many laid-out thin-film electron emitter elements 301 as pixels composing the display apparatus or sub-pixels composing a color display apparatus.
Assume that a negative voltage pulse (xe2x88x92V1) is applied to the row electrode 310 on the R2th row and a positive voltage pulse (+V2) is applied to the column electrode 311 on the C2th column. In this case, since a voltage of (V1+V2) is applied to the thin-film electron emitter element 301 at an intersection (R2, C2) of the row electrode 310 on the R2th row and the column electrode 311 on the C2th column, the thin-film electron emitter element 301 emits electrons.
The emitted electrons are accelerated and then radiated to phosphors, causing the phosphors to emit lights.
In a line-at-a-time operation, a pixel emits a light during a period in a unit time. The ratio of the period to the unit time is referred to as a duty ratio, which is inversely proportional to a scanning-line count N, that is, the number of row electrodes 310. That is, the brightness of the screen is proportional to 1/N.
As indicated in the 1997 SID International Symposium Digest of Technical Papers, pages 123 to 126 (May 1997), however, the brightness of a light emitted during application of a voltage pulse in a display apparatus employing thin-film electron emitter elements 301 and phosphors is sufficiently high so that enough screen brightness is obtained even if a line-at-a-time operation is adopted.
In addition, a relation between the applied voltage and the brightness exhibits a steep threshold characteristic. Thus, even for N of about 1,000, passive-matrix addressing results in sufficient contrast.
That is, unlike a liquid-crystal display apparatus, in the case of a display apparatus employing thin-film electron emitters, it is not necessary to provide a switching element on each pixel in order to improve the threshold characteristic and to increase the duty ratio of the light emitting period.
Next, let us find a dissipation power of drivers in the configuration shown in FIG. 22.
The dissipation power is a power consumed in electrically charging and discharging a capacitance employed in thin-film electron emitter elements 301 being driven by the driver. Thus, the dissipation power does not contribute to light emission by the thin-film electron emitter element 301. Assume that the capacitance of the capacitor employed in a thin-film electron emitter element 301 is Ce, the number of column electrodes 311 is M and the number of row electrodes 310 is N. In this case, the dissipation power for a one-time application of a pulse with an amplitude of Vr to a row electrode 310 is expressed by Eq. (1) as follows.
Dissipation power =Mxc2x7Cexc2x7Vr2xe2x80x83xe2x80x83(1)
Let a symbol f denote a field frequency, which is the number times the screen is updated in 1 second. In this case, the dissipation power Pr of the N row electrodes 310 in 1 second is expressed by Eq. (2) as follows:
Pr=fxc2x7Nxc2x7Mxc2x7Cexc2x7Vr2xe2x80x83xe2x80x83(2)
Since N thin-film electron emitter elements 301 are connected to each column electrode 311, the dissipation power Pc, which is incurred when a pulse voltage is applied to all M column electrodes 311, is expressed by Eq. (3) as follows:
Pc=fxc2x7Mxc2x7Nxc2x7(Nxc2x7Cexc2x7Vc2)xe2x80x83xe2x80x83(3)
where a symbol Vc is the amplitude of the voltage pulse applied to the column electrodes 311.
As is obvious from Eqs. (2) and (3), the expression of the dissipation power Pc has an additional multiplicand N in comparison with the dissipation power Pr. This is because, in 1 field period, N consecutive pulses are applied to the column electrodes 311 where the field period is a period during which the screen is updated once.
If the voltage pulse with the amplitude Vc is applied only to m column electrodes 311 among the M column electrodes 311, the dissipation power can be obtained by substituting m for M in Eq. (3).
As an example, assume the following representative values: f=60 Hz, N=480, M 32 1,920, Ce=0.1 nF and Vr=Vc=4V. In this case, the dissipation powers are found to be Pr =0.09 W and Pc =42 W.
Since the power consumption of the thin-film electron emitter elements 301 themselves is about 1.6 W, the total power consumption is about 44 W, a value causing no problem in practical use.
When it is desired to further reduce the power consumption, however, reduction of the dissipation power Pc accompanying application of the data pulses is obviously a known effective method.
As described above, when the display apparatus is used as a display apparatus corresponding to a CRT, even with the conventional technology, there is no power-consumption problem.
However, a feature of the display apparatus employing a matrix of thin-film electron emitters is its feasible implementation as a thin display apparatus.
Such a thin display apparatus also has an application as a portable display apparatus. In this application, it is desired to further reduce the power dissipation.
In addition, the effective impedance of each thin-film electron emitter element 301 is small. That is, since a relatively large current flows to the thin-film electron emitter element 301, when the matrix of thin-film electron emitters is driven in a line-at-a-time operation, currents flow through a number of thin-film electron emitter elements pertaining to an electrode, raising problems such as the fact that brightness uniformity over the entire screen cannot be obtained unless resistivity along each feeding line is reduced.
The same problems are also encountered in a display apparatus employing an electro-luminescence(EL) array or a matrix of organic EL elements, which are also called organic light-emitting diodes (OLEDs).
The present invention aims at solving the problems by providing a technology of reducing power consumption in a display apparatus.
The present invention also aims at providing a technology of improving an image quality in a display apparatus.
The above and other objects as well as novel characteristics of the present invention will become apparent from the description and accompanying diagrams given in this specification.
First of all the principle of operation of the present invention is explained.
FIG. 1 is a diagram showing a typical configuration of a thin-film matrix of a display apparatus provided by the present invention in a simple and plain manner.
In the conventional configuration, only a thin-film electron emitter element 301 is connected at a location in close proximity to a region where a row electrode 310 crosses a column electrode 311. In the case of the present invention, however, a pixel transistor 302 and a thin-film electron emitter element 301 are connected at a location in close proximity to a region where a row electrode (a first signal line of the present invention) 310 crosses a column electrode (a second signal line of the present invention) 311, and a driving voltage is supplied to one of the electrodes (the base electrode 13) of the thin-film electron emitter element 301 by way of the pixel transistor 302 as shown in FIG. 1.
To put it in detail, the gate of the pixel transistor 302 is connected to the row electrode 310 and the source of the transistor 302 is connected to the column electrode 311. The drain of the transistor 302 is connected to the one of the electrodes (the base electrode 13) of the thin-film electron emitter element 301.
The other electrode (the top electrode 11) of the thin-film electron emitter element 301 is connected to a top-electrode driver 45.
It should be noted that, if a TFT (thin-film transistor) is employed as the pixel transistor 302, the drain and the source thereof are virtually not distinguished from each other. In this specification, however, the terms source and drain are used for convenience sake even in the case of a TFT (thin-film transistor).
In this specification, a region surrounding or in the vicinity of a cross point of a row electrode 310 and a column electrode 311 is referred to as an intersection region. An region enclosed by a row electrode 310 and a column electrode 311 is referred to as a pixel in the following description. The transistor 302 provided in the pixel region is referred to as a pixel transistor.
In the case of a color display apparatus, a combination of red, blue and green sub-pixels actually constitutes a pixel. In the case of a color display apparatus, however, by a pixel, a sub-pixel is implied in this specification. Word xe2x80x9cdotxe2x80x9d is also used to denote a pixel or a sub-pixel.
The thin-film electron emitter element 301 at an intersection region (R2,C2) of the row electrode 310 on the R2th row and the column electrode 311 on the C2th column operates as follows.
A pulse voltage is applied to the row electrode 310 on the R2th row to turn on the pixel transistor 302 (or to put the pixel transistor 302 in a conductive state).
At the same time, if a pulse having a voltage amplitude of V2 is applied to the column electrode 311 on the C2th column, a voltage of (Vcom xe2x88x92V2xe2x88x92xcex94V) is applied to the thin-film electron emitter element 301 at the intersection region (R2,C2), causing the thin-film electron emitter element 301 to emit electrons.
A symbol Vcom denotes the output voltage of the top-electrode driver 45 and a symbol xcex94V denotes a voltage drop along the resistor (or the output impedance) of the pixel transistor 302.
At dots connected to the row electrodes 310 on the R1th and R3th rows, the pixel transistors 302 are in an OFF state. Thus, no voltages are applied to the thin-film electron emitter elements 301 connected to these pixel transistors 302 and the thin-film electron emitter elements 301 therefore emit no electrons. In this way, the present invention displays an image in accordance with the line-at-a-time scheme.
The following description explains estimation of a dissipation power consumed by drivers in an application using the present invention.
The dissipation power Pr of a row-electrode driver 41 is expressed by Eq. (4) as follows:
Pr=fxc2x7Nxc2x7Mxc2x7Cgsxc2x7Vr2xe2x80x83xe2x80x83(4)
where a symbol Vr denotes the amplitude of a voltage pulse applied to a row electrode 310 and a symbol Cgs denotes the stray capacitance between the gate and the source of the pixel transistor 302 at each dot.
Normally, the stray capacitance Cgs is about 1 pF. Since this stray capacitance Cgs is about {fraction (1/100)} to {fraction (1/1000)} of the capacitance Ce of the thin-film electron emitter element 301, the dissipation power Pr is also about {fraction (1/100)} to {fraction (1/1000)} of a dissipation power according to the conventional method.
On the other hand, the dissipation power Pc of a column-electrode driver 42 is expressed by Eq. (5) as follows:
Pc=fxc2x7Mxc2x7Nxc2x7Cexc2x7Vc2+fxc2x7Mxc2x7Nxc2x7(Nxe2x88x921)xc2x7Cdsexc2x7Vc2xe2x80x83xe2x80x83(5)
In Eq. (5), the first term is a term attributed to dots at which the pixel transistors 302 are each put in a conducting state and the second term is a term attributed to other dots, that is, dots at which the pixel transistors 302 are each put in a non-conducting state.
In Eq. (5), a symbol Vc denotes the amplitude of a voltage pulse applied to a column electrode 311 and a symbol Cdse denotes a combined capacitance of the capacitance Ce of a thin-film electron emitter element 301 and the stray capacitance Cds between the drain and the source of a pixel transistor 302. The combined capacitance Cdse is expressed by Eq. (6) as follows:
Cdse=(1/Cds+1/Ce)xe2x88x921=Cds/(Cds/Ce+1)xe2x80x83xe2x80x83(6)
Normally, the stray capacitance Cds is about 1 pF. Since this stray capacitance Cds is about {fraction (1/100)} to {fraction (1/1000)} of the capacitance Ce of the thin-film electron emitter element 301, the combined capacitance Cdse is about equal to the stray capacitance Cds, which is about {fraction (1/100)} to {fraction (1/1000)} of the capacitance Ce.
Thus, the dissipation power Pc can be reduced to about 1/N of the dissipation power according to the conventional method.
In this way, the dissipation powers of the row-electrode drivers 41 and the column-electrode driver 42 according to the present invention can be reduced considerably.
In addition, since the load capacitance of each of the row-electrode drivers 41 and column-electrode drivers 42 is reduced, requirement to the row-electrode driver 41 and the column-electrode driver 42 are relaxed. As a result, the scheme provided by the present invention contributes to cost reduction of the row-electrode driver 41 and the column-electrode driver 42.
In the display embodiment, there have been proposed and/or implemented techniques for controlling the operation of each pixel by using a transistor provided on the pixel. A technique for controlling the operation of a pixel by using a transistor provided on the pixel is referred to as the active-matrix addressing scheme.
The active-matrix addressing scheme is widely adopted in liquid-crystal display apparatuses. This is because, since the threshold characteristic of the transmittance with respect to the applied voltage of liquid-crystal element is not steep, the adoption of the passive-matrix addressing scheme will decrease the contrast.
The active-matrix addressing technique lengthens the period to apply a voltage to each pixel. In other words, by increasing the duty ratio, the contrast is improved.
On the other hand, the operating mode of each pixel adopted by the present invention is a line-at-a-time scheme. That is, the duty ratio of an emitted light is 1/N and, hence, the operating mode is essentially different from the active-matrix addressing technique adopted in a liquid-crystal display apparatus. Here, the line-at-a-time scheme includes xe2x80x9cone-line-at-a-timexe2x80x9d and xe2x80x9ctwo-line-at-a-timexe2x80x9d schemes; in the latter scheme, the display area is divided into two areas, in each of which the one-line-at-a-time scheme is used, and the duty ratio is 2/N.
As described in the 1999 SID International Symposium Digest of Technical Papers, pages 438 to 441 (May 1999), in an electro-luminescence (EL) display apparatus adopting the active-matrix addressing scheme, a pixel is implemented by a combination of at least 2 transistors and a storage capacitance.
One of the transistors is used for controlling the flow-in and the flow-out of electric charge to and from the storage capacitance. The other transistor controls the light emission from the EL element of the pixel in accordance with the voltage of the storage capacitance.
In this way, the light emission period of the EL element of each pixel, that is, the duty ratio, is increased to give a high luminance. Thus, this technique is also essentially different from the present invention.
As a typical application of the active-matrix addressing scheme to a field emission display (FED) apparatus, a transistor is formed at each dot of a matrix of surface-conduction electron emitters as is described in Japanese publication of unexamined applications No.9-219164.
In this typical application disclosed to the public, in order to prevent a current emitted by a surface-conduction electron emitter from varying from dot to dot, the magnitudes of the currents are made uniform by taking advantage of a constant-current characteristic of a transistor provided at each pixel.
FIG. 2 is a diagram showing a relation between the drain current ID and the drain-source voltage VDS of a MOS transistor under a condition of a constant gate voltage.
It is obvious from FIG. 2 that, as the drain-source voltage VDS exceeds a predetermined level, that is, the boundary between a non-saturation region and a saturation region, the drain current ID stays at an all but constant value independently of the voltage VDS.
Also for an FED apparatus employing a field-emission array (FEA) as a source of electrons, there has been proposed a scheme in which a transistor is provided at each dot as is described in the Proceedings of the 5th International Display Workshops, pages 667 to 670 (December 1998). Much like the display apparatus disclosed to the public as described above, each pixel transistor is operated in the saturation region. The constant-current-characteristic in the saturation region is used to reduce the amount of noise and to stabilize the emitted current.
However, the technique of operating each pixel transistor in its saturation region to take advantage of the constant-current characteristic of the transistor as is disclosed in the announced display apparatuses has a problem caused by a big effect of variations in pixel-transistor characteristic.
The problem is described below.
In general, the drain current Id(sat) in the saturation region of the MOS transistor shown in FIG. 2 can be expressed by Eq. (7) as follows:
ID(sat)=kxc2x7(VGSxe2x88x92VT)2xe2x80x83xe2x80x83(7)
where a symbol VGS denotes the voltage between the gate and the source, a symbol VT denotes a threshold value and a symbol k denotes a quantity that can be expressed by Eq. (8) in terms of a mobility xcexcn of a semiconductor composing the MOS transistor, a gate capacitance Cox and geometrical parameters (W/L) of the MOS transistor as follows:
xe2x80x83k=(1/2)xcexcnCox(W/L)xe2x80x83xe2x80x83(8)
In actual MOS transistors, there are variations in threshold value VT from transistor to transistor. Since the drain current ID (sat) in the saturation region is proportional to the square of (VGSxe2x88x92VT), the effect of the variations in threshold value VT from transistor to transistor is big.
Thus the technique of operating each pixel transistor in its saturation region to take advantage of the constant-current characteristic of the transistor has a problem of a necessity to form pixel transistors with a high degree of uniformity in order to overcome the big effect of the variations in threshold value VT from transistor to transistor.
If a thin-film transistor (TFT) made of a material such as amorphous silicon or poly-silicon is employed as a pixel transistor, it is particularly difficult to keep the uniformity of the pixel TFTs. The amorphous silicon and the poly-silicon are referred to hereafter simply as a-Si and poly-Si respectively.
In the present invention, in order to reduce the effect of variations in characteristic from transistor to transistor, each pixel transistor 302 is operated in its non-saturation region. That is, each pixel transistor 302 is operated in a region where the drain current ID varies greatly with the voltage VDS applied between the drain and the source of the pixel transistor 302.
In the characteristic of FIG. 2 representing a relation between the drain current ID and the voltage VDS between the drain and the source, the reciprocal of the slope of the curve in the non-saturation region, that is, the effective resistance R or the output impedance, is expressed by Eq. (9) as follows:                     R        =                                            (                                                ⅆ                                      I                    D                                                                    ⅆ                                      V                    DS                                                              )                                      -              1                                =                                    {                              2                ⁢                                  k                  ⁡                                      (                                                                  V                        GS                                            -                                              V                        T                                                              )                                                              }                                      -              1                                                          (        9        )            
Since Eq. (9) obviously indicates that the characteristic in the non-saturation region is dependent only on the reciprocal of (VGSxe2x88x92VT), the effects of variations in threshold value VT from transistor to transistor is small in comparison with the effect on the drain current ID (sat) in the saturation region.
Next, assume a case in which the thin-film electron emitter element (or the MIM electron emitter element) 301 is connected in series to the pixel transistor 302 as shown in FIG. 1 and an external voltage Vo is applied to the entire serial connection. In this case, the effect of variations in output impedance R from transistor to transistor on a current flowing to the thin-film electron emitter element 301 is estimated as follows.
Id=f (V) indicates that the diode current Id of the thin-film electron emitter element 301 is a function of voltage V. Conversely speaking, V=fxe2x88x921 (Id) Let symbols I and I+xcex94I denote currents that flow when the output impedance of the pixel transistor is R and (R+xcex94R) respectively where a symbol xcex94R denotes variations xcex94R in characteristic from transistor to transistor. In this case, Eq. (10) holds true as follows:                                                                                           Δ                  ⁢                                      xe2x80x83                                    ⁢                  I                                I                            =                                                (                                                            Δ                      ⁢                                              xe2x80x83                                            ⁢                      R                                                              R                      +                                              Δ                        ⁢                                                  xe2x80x83                                                ⁢                        R                                                                              )                                /                                  (                                      I                    +                    α                                    )                                                                                                        α              =                                                r                  e                                                  R                  +                                      Δ                    ⁢                                          xe2x80x83                                        ⁢                    R                                                                                                                                          r                e                            =                                                ⅆ                  V                                                  ⅆ                                      I                    d                                                                                                          (        10        )            
where xcex1=re/(R+xcex94R) and
re=dV/dId, the derivative of the inverse function fxe2x88x921 with respect to Id.
Thus, by setting the output impedance (R+xcex94R) of the pixel transistor 302 at a value smaller than the differential resistance re (at the operation point) of the thin-film electron emitter element 301, the relation xcex1xe2x89xa71 holds true. In this case, Eq. (11) can be derived from Eq. (10) as follows:                                           Δ            ⁢                          xe2x80x83                        ⁢            I                    I                ≤                              1            2                    ⁢                      (                                          Δ                ⁢                                  xe2x80x83                                ⁢                R                                            R                +                                  Δ                  ⁢                                      xe2x80x83                                    ⁢                  R                                                      )                                              (        11        )            
In this way, the effects of variations xcex94R in characteristic from transistor to transistor on the uniformity of the displayed picture can be made even smaller. In other word, the allowance of the variations xcex94R in characteristic from transistor to transistor increases, making the fabrication process easy to carry out.
In another technique of reducing the variations xcex94R in characteristic from transistor to transistor, the pixel transistor 302 is operated in the non-saturation region and a constant-current circuit is used as the column-electrode driver 42.
In this case, the pixel transistor 302 is employed as a switching element with an on-resistance of R. Even if the effective resistance R of the pixel transistor 302 changes, the current flowing through the thin-film electron emitter element 301 is set by the column-electrode driver 42 at a constant magnitude.
This technique is particularly effective for a case in which a thin-film transistor (TFT) made of a material such as a-Si or poly-Si is employed as the pixel transistor 302 and a single-crystal silicon (Si) substrate is used for the column-electrode driver 42. This is because, by using a single-crystal silicon (Si) substrate, variations in characteristic from transistor to transistor can be suppressed with ease.
The use of a constant-current circuit as the column-electrode driver 42 is specially effective for a case in which variations in relation B=h (I) between the element current I and the brightness B is small in comparison with variations and fluctuations appearing in the relation B=g (V) between the applied voltage V and the brightness B.
The elements adopting the configuration described above include an organic EL (organic electro-luminescence) element, also called an organic light-emitting diode (OLED), and a light-emitting diode (LED).
Representatives of the present invention described in this specification are explained briefly and simply as follows.
The present invention provides a display apparatus comprising a display element,
said display element comprising a first substrate, a frame element, and a second substrate having phosphors, and a space enclosed by said first substrate, said frame element and said second substrate being a vacuum environment;
said first substrate comprising a plurality of transistor elements, a plurality of electron emitter elements, a plurality of first signal lines stretched in a first direction, and a plurality of second signal lines stretched in a second direction perpendicular to said first direction;
each of said electron emitter elements being provided for one of said transistor elements, having a structure comprising a base electrode, an insulator and a top electrode stacked as layers placed one on another in this order of enumeration, and emitting electrons when a positive-polarity voltage is applied to said top electrode;
wherein each of said transistor elements and each of said electron emitter elements are provided in each intersection region of said plurality of first signal lines and said plurality of second signal lines.
In addition, the present invention also provides a display apparatus comprising a display element,
said display element comprising a first substrate, a frame element, and a second substrate having phosphors, and a space enclosed by said first substrate, said frame element and said second substrate being a vacuum environment;
said first substrate comprising a plurality of transistor elements, a plurality of electron emitter elements, a plurality of first signal lines stretched in a first direction, and a plurality of second signal lines stretched in a second direction perpendicular to said first direction;
each of said electron emitter elements being provided for one of said transistor elements, having a structure comprising a base electrode, an insulator and a top electrode stacked as layers placed one on another in this order of enumeration, and emitting electrons when a positive-polarity voltage is applied to said top electrode;
wherein each of said transistor elements is provided in each region enclosed by said plurality of first signal lines and said plurality of second signal lines.
Furthermore, the present invention also provides a display apparatus comprising a display element,
said display element comprising a first substrate, a frame element, and a second substrate having phosphors, and a space enclosed by said first substrate, said frame element and said second substrate being a vacuum environment;
said first substrate comprising a plurality of transistor elements, a plurality of electron emitter elements, a plurality of first signal lines stretched in a first direction, and a plurality of second signal lines stretched in a second direction perpendicular to said first direction;
each of said electron emitter elements being provided for one of said transistor elements, having a structure comprising a base electrode, an insulator and a top electrode stacked as layers placed one on another in this order of enumeration, and emitting electrons when a positive-polarity voltage is applied to said top electrode;
wherein a control electrode of each of said transistor elements is electrically connected to one of said first signal lines,
a first electrode of each of said transistor elements is electrically connected to one of said second signal lines, and
a second electrode of each of said transistor elements is electrically connected to said base electrode of said electron emitter element associated with said transistor element.
Moreover, the present invention is characterized in that an output impedance of each of said transistor elements is smaller than a differential resistance in an operation region of one of said electron emitter elements.
In addition, the present invention further comprises a first driving means for supplying a driving voltage to each of said first signal lines, and a second driving means for supplying a driving voltage to each of said second signal lines; and wherein said second driving means has a constant-current circuit.
Furthermore, the present invention also provides a display apparatus comprising a display element, a first driving means and a second driving means;
said display element comprising a first substrate, and a second substrate having phosphors;
said first substrate comprising a plurality of transistor elements, a plurality of electron emitter elements each provided for one of said transistor elements, a plurality of first signal lines stretched in a first direction, and a plurality of second signal lines stretched in a second direction perpendicular to said first direction;
wherein said first driving means supplies a driving voltage to each of said first signal lines,
said second driving means supplies a driving voltage to each of said second signal lines,
a control electrode of each of said transistor elements is electrically connected to one of said first signal lines,
a first electrode of each of said transistor elements is electrically connected to one of said second signal lines,
a second electrode of each of said transistor elements is electrically connected to said base electrode of said electron emitter element associated with said transistor element, and said second driving means has a constant-current circuit.
Moreover, the present invention also provides a display apparatus comprising a display element, a first driving means and a second driving means;
said display element comprising a first substrate;
said first substrate comprising a plurality of transistor elements, a plurality of electro-luminescence elements each provided for one of said transistor elements, a plurality of first signal lines stretched in a first direction, and a plurality of second signal lines stretched in a second direction perpendicular to said first direction;
wherein said first driving means supplies a driving voltage to each of said first signal lines,
said second driving means supplies a driving voltage to each of said second signal lines,
a control electrode of each of said transistor elements is electrically connected to one of said first signal lines,
a first electrode of each of said transistor elements is electrically connected to one of said second signal lines,
a second electrode of each of said transistor elements is electrically connected to a first electrode of said electro-luminescence element associated with said transistor element,
and said second driving means has a constant-current circuit.
In addition, the present invention also provides a display apparatus comprising a display element, a first driving means and a second driving means;
said display element comprising a first substrate;
said first substrate comprising a plurality of transistor elements, a plurality of light-emitting diode elements each provided for one of said transistor elements, a plurality of first signal lines stretched in a first direction, and a plurality of second signal lines stretched in a second direction perpendicular to said first direction;
wherein said first driving means supplies a driving voltage to each of said first signal lines,
said second driving means supplies a driving voltage to each of said second signal lines,
a control electrode of each of said transistor elements is electrically connected to one of said first signal lines,
a first electrode of each of said transistor elements is electrically connected to one of said second signal lines,
a second electrode of each of said transistor elements is electrically connected to a first electrode of said light-emitting diode element associated with said transistor element,
and said second driving means has a constant-current circuit.
Furthermore, the present invention is characterized in that each of said transistor elements is a thin-film transistor, which is operated in a non-saturation region thereof.